Method for producing a modeling system for vessel deformations

ABSTRACT

Local heating of a first hollow body which is suited for conducting liquid and is comprised, at least in one or more partial areas, of a flexible, thermoplastically deformable material. The local heating is effected on at least one of the partial areas until the thermoplastically deformable material softens. The invention also involves subjecting this first hollow body to the action of pressure that is great enough to cause a deformation at the heated location, whereby the size of the deformation is determined by the duration of the pressure applied and/or by the intensity of the pressure applied.

The invention relates to a method for the production of a modelingsystem for vessel malformations, in particular aneurysms and stenoses,as well as modeling systems made according to this method and their usein the medical sector.

Diseases of the cardiovascular system caused by unhealthy eating habits,stress and/or a physical predisposition count among the most frequentcauses of death encountered in society today. In the field ofcardiovascular diseases the congenital or acquired vessel malformationssuch as for example aneurysms or local vessel constrictions (stenoses)are found rather frequently.

Aneurysms are thin-walled protuberances encountered in the vascularsystem which are caused, inter alia, by a weakness of the wall of theaffected vessel. Such aneurysms are treated by surgical-operativemethods (e.g. “aneurysm clip”) or by means of endovascular techniques.The endovascular treatment of aneurysms involves the introduction ofmaterial needed for the occlusion of the aneurysm through the vascularsystem and transfer of said material to the point where the aneurysm tobe occluded is located. In that location the material (e.g. polymershardening in the blood, fibers of various kind or thrombosizing spirals)is placed in position and the catheter removed from the blood vesselsystem. Another therapy method is the placement of stents (i.e. vascularendoprostheses) over the branching point of the aneurysm in the relevantblood vessel. If successful such a method enables the normal flow ofblood to be restored while preventing blood from entering or restrictingthe blood flow into the aneurysm so that the blood present in theaneurysm coagulates. If thought expedient, tissue sclerotizationmaterials (“tissue adhesives”) may additionally be used. It is theobjective of all these measures to bring about a stable occlusion of theaneurysm through the cicatrization of the thrombus that has formed.

Transferring the occlusion agent to the destination site calls for greatexpertise all the more so since aneurysms not only occur in the area ofthe large pathways but are also found frequently in difficult to accessvessel sections such as the cranial or cerebral arteries. Mistakes madewhen transferring the catheter or placing the occluding material areassociated with great risks for the patient because vessel wallinjuries, fragments of broken-off occlusion spirals floating in theblood stream, occluding material flushed out of the anneurysm andentering the blood vessel system or washed-out thrombs will mostprobably cause embolism and tissue infarcts which in the worst case mayresult in the death of the patient.

For the purpose of training endovascular manipulation and the placementof the occluding materials it is known to make use of a model system foraneurysms that consists of a glass tube system with bulging-outsections; said system can be filled with liquid. This system can be usedto try out new surgical techniques before such methods are applied toanimals or human beings. Furthermore, inexperienced surgeons may usethis system to exercise themselves in endovascular-therapeutictechniques.

A disadvantage of this system is that the glass tubes and bulgesformed-out in the glass tubes have properties entirely different fromthe characteristics of natural blood vessels and aneurysms. Inparticular, the glass tube system differs from blood vessels in that itlacks elasticity and has a much greater stability so that even when theocclusion materials have been successfully placed within the glass tubesystem it cannot be ensured that this technique may also be applied invivo without causing health risks for the patient. Another drawback ofthis model system is that it is very expensive due to the fact that theglass tubes and deformations must be handblown and manually formed out.Lower-priced non-elastic vessel models made of plexiglass or hardplastic material basically suffer similar disadvantages.

A comparable problem area is linked with the endovascular-therapeutictreatment of stenotic vessel sections: vascular stenoses are congenitalor acquired constrictions of the vessels. The most common cause ofacquired vessel stenoses are atherosclerotic vessel malformationscharacterized by hardening, thickening and loss of elasticity of theaffected vessels and ultimately leading to a constriction of the vesselvolume. Aside from and supplementary to medicational therapy formsendovascular-therapeutic techniques are primarily applied such as theballoon dilatation or placement of stents to be used as vascularsupporting elements to keep the lumen open, as a rule a combination ofboth methods. In this case as well modeling systems are needed for thedevelopment and testing of suitable therapy forms due to the fact thatthe known rigid systems are of very little use only when it comes toimitate or reproduce actual in vivo conditions.

In view of the drawbacks associated with the state of the art it is thusthe object of the invention to provide a cost-effective modeling systemfor vessel malformations which imitates or reproduces the properties ofblood vessels and vessel deformations better than the model systems ofthe known state of the art.

This objective is to be achieved in accordance with the invention by amethod for the production of a modeling system for vessel malformationsinvolving the following steps:

-   -   a) local heating of a first hollow body which is suited for        conducting liquid and consists, at least in one or more partial        areas, of a flexible, thermoplastically deformable material,        such local heating being effected on one or more partial areas        until the thermoplastically deformable material softens, and    -   b) subjecting the hollow body to a pressure that is high enough        to cause a deformation at the heated location, with the size and        shape of the deformation being governed by the duration of the        pressure applied and/or by the intensity of the pressure        applied.

The deformations produced by the method according to the invention may,in particular, be used to recreate deformations of the vessel wall suchas aneurysms or for the replication of expanded vessel segments.

The method, therefore, lends itself to produce deformations that, forexample, have a wall thickness severely reducing from the base towardsthe dome and whose lacerability, due to the flexibility of thethermoplastically deformable material, is more similar to that ofaneurysms than can be achieved with traditional modeling systems.Furthermore, with the aid of the inventive method models of vesselstenoses can be produced; in this case the deformations will representthe unchanged segments of the vessel whereas the non-deformed partialareas of the hollow body correspond to the stenotic vessel sections.

Other than with the rigid vessel models the models provided by themethod is according to the invention will not only reproduce thedifferences in size of the inner lumen but also differences inelasticity existing between the stenotic and non-stenotic vessel areas.As a rule, for the reproduction of stenoses a softer and more flexibleplastic material (that has better thermoplastic deformabilitycharacteristics requiring less force to be exerted) is used to simulateexpansion characteristics.

As a result of the flexibility of the thermoplastically deformablematerial the elasticity of the vessel system is reproduced so that themodel system generated in accordance with the invention reflects thesituation actually existing in the body more precisely than can beachieved by the customary artificial systems available according to thestate of the art. For example, aside from the shaping of vesselmalformations their elasticity and fragility can also be reproduced andin this way differences which exists with respect to the “physiological”vessel segments can be simulated by selecting materials and materialproperties suited for the relevant purpose.

When the deformation has been shaped out and the thermoplastic materialcooled down to a temperature lower than its softening point the modelingsystem according to the invention may at once be filled with a liquidand put to use, for example to try out or study endovascular-therapeutictechniques.

However, when producing the system for stockkeeping purposes it isthought expedient that, after manufacture in accordance with theinvention has been completed, the hollow space of the first hollow bodyis filled with air or inert gas and sealed off so as to be air-tight. Inthis manner the deformations will remain stable and retain theiroriginal shape even when stored for a prolonged period of time (e.g.lasting severable months). In such cases, before it is used for theintended purpose the modeling system produced in accordance with theinvention will be opened by cutting the closure locations off or open.Expediently, the closure is effected by fusing or bonding together theopenings of the hollow body filled with pressurized gas. Nevertheless,basically acceptable is every method by means of which the stable shapeof the produced deformations can be warranted.

It will also be appropriate if at least the produced deformation andpreferably the entire first hollow body are designed so as to betranslucent or basically transparent, so that, for example, it may beeasily viewed from the outside whether a tested method has beensuccessful. Especially expedient in this context is the use of a firsthollow body that is translucent in its entirety and, in particular,basically transparent for the purpose of implementing the methodaccording to the invention.

As per an especially expedient embodiment of the invention the entirefirst hollow body is made of a flexible material because the difficultylinked with maneuvering endovascular catheters intravascularly is mainlydue to the fragility and elasticity of the vascular system. Such anembodiment offers the advantage that not only the area where thedeformation is situated reflects characteristics quite similar to thosefound in the organism but all other partial areas of the hollow body aswell. In this manner it is possible, for instance, to determine alreadyin the stage of learning endovascular techniques requiring amicro-catheter to be moved towards the site of the deformation (forexample an artificial aneurysm) whether an excessively traumatizingmanipulation occurs. Furthermore, modeling systems produced by means offully flexible first hollow bodies will simulate the characteristics ofvessels through which blood circulates, for instance “surge tankeffects” etc. Through the selection of suitable pumping systemspulsatile systolic-diastolic liquid pressures may be generated as theyare actually occurring in the organism. Moreover, a particularlyexpedient hollow body in accordance with the invention is embedded ina—preferably hyaline—gel, for example gelatine, or in a plastic materialhaving similar properties. This embodiment is especially suited tosimulate the natural suspension of vessels and reticular vessel in thebody.

In accordance with another preferred embodiment the entire first hollowbody consists of a thermoplastic material. This embodiment is especiallycost-effective and moreover allows deformations to be produced in anydesired place of the first hollow body. Especially preferred in thiscontext is an embodiment in that the entire first hollow body consistsof a flexible, thermoplastically deformable material that, in addition,is transparent.

Basically, any kind of thermoplastically deformable material that can beprocessed without difficulty may be used. Particularly suitable asthermoplastically deformable materials are PVC (polyvinyl chloride), PUR(polyurethane), PP (polypropylene) or PE (polyethylene) because thesemay also be of flexible design. PVC is an especially preferred material.Through the selection of the material and dimensioning of the wallthickness of the first hollow body the above mentioned average personskilled in the art is capable of varying the elasticity of the modelwith a view to simulating certain vessels, reticular vessel structuresor vascular malformation.

The local heating is preferably brought about by the local effect causedby a hot liquid, preferably a lipophilic liquid having a high boilingpoint, such as for example an oil; through the local effect caused by aflame, preferably a flame generated by a gas torch; through the use of ahot wire, especially a hot wire spiral that is applied locally from theinside or outside to the wall of the hollow body; or through exposingthe body locally to microwaves. However, any kind of heating effect maybasically be put to use provided it is capable of bringing about a localheating of the thermoplastic material associated with a softeningeffect. In this context, heating effected with the help of a gas flameis particularly cost-effective. On the other hand, using microwaves orhot liquids (for example paraffin oil) to heat the first hollow bodyenables a particularly precise thermal regulation to be achieved.

In accordance with an expedient embodiment the first hollow bodyrepresents a system of two-dimensionally arranged, communicatingpathways (that may differ from each other to simulate the situationencountered in a natural vascular system, for instance with respect todiameter and/or length as well as shape which may be of winding orprimarily elongated configuration), or part of such a system. Forexample, the first hollow body may thus be produced in a mannerotherwise employed in the manufacture of printed circuit boards bysticking two, in particular flexible, plastic foils together sectionallyby bonding or welding methods with the communicating pathways formingthe vascular system or part thereof being left free. In this way atwo-dimensional model of a vessel system is created said system beingsuitable to practice moving objects through branching vascular pathwaysin a precise target-seeking manner. Particularly, this method allowsproducing in a simple manner vessel models of winding configuration. Forthe manufacture of such a system a tear-resistant foil may preferably beused, said foil having, for example, a wall thickness roughlycorresponding to that of average vessel walls.

In accordance with another preferred embodiment the first hollow bodyrepresents a hose, a two- or three-dimensional system of communicating(which means connected so as to be conductive) hoses (that may differfrom each other to simulate the situation encountered in a naturalvascular system, for instance with respect to diameter, wall thicknessand/or length as well as shape which may be of winding or primarilyelongated configuration), or part of such a system. In its most simpleform as a hose the modeling system is especially cost-effective. On theother hand, a system of communicating hoses permits two- orthree-dimensional models of the vascular system or parts thereof to bereproduced.

For the creation of the deformations any kind of pressure generation maybe employed (for example, through hydrostatic, pneumatic or mechanicalmeans). Pneumatically produced pressure is particularly suited becausethe generation of such a pressure is simple and inexpensive. Producingpressure hydrostatically is particularly suitable because pressuregenerated in this way simulates conditions prevailing during thedevelopment of natural aneurysms.

In accordance with an especially expedient embodiment of the inventivemethod the first hollow body, prior to local heating, is placed at leastpartially into a second hollow body consisting of a material that cannotbe thermoplastically deformed, with at least a partial area of thesecond hollow body accommodating at least a partial area of the firsthollow body in a form-closed manner. The shape of the second hollow bodyin this case is expediently adapted to the form of the first hollow body(hose, system of communicating hoses, two-dimensional system ofcommunicating pathways or part thereof). The second hollow body may thusbe designed as a thermoplastically non-deformable tube of which at leasta partial area is suited to accommodate in a form-closed manner a firsthollow body having the form of an appropriately shaped hose. In thisway, the hose can be shaped out in a defined manner after it has beenplaced into the tube.

It is thus especially expedient if the second hollow body has at leastone cut-out, in particular one or several cut-outs that have anellipsoidal or annular shape. In this embodiment of the invention thesecond hollow body is preferably suited for the production of systemsmodeling pathological vessel ballooning, in particular aneurysms. Inthis manner, deformations whose position can be precisely determined onthe first hollow body can be created by heating the partial areas of thefirst hollow body, said areas being arranged underneath the cut-outswhen part of or the entire first hollow body is accommodated within partof or the entire second hollow body. In this way it is possible topredetermine exactly the type of aneurysm and its neck diameter byselecting a defined (for example ellipsoidal or annular) cut-out havinga defined diameter. Various types of deformations (for example fusiformor aciniform aneurysms) of various diameters can thus be produced.

It may be expedient in this context if the second hollow body (forinstance made of glass, thermoplastically non-deformable plastic ormetal) consists of a single piece with the first hollow body remaininginside the second after the deformations have been produced. In this waytwo-shell models of vascular malformations can be created wherein theouter, second hollow body not only may determine the starting form andsize of the deformations but also the shape of the first hollow body:For example a first hollow body designed as a customary hose ofthermoplastic material is placed in a second hollow body which has theshape of a bent tube provided with cut-outs. This will enable theconvolutions of the vessel bearing the malformation which are situatedbefore or after the malformation to be exactly reproduced without thenecessity of having to mount a first hollow body which is appropriatelypreformed. This implementation form of the method according to theinvention is particularly inexpensive because first hollow bodies ofespecially simple construction (e.g. conventional hoses) andprefabricated second hollow bodies (e.g. made of plexiglass, glass ormetal) can be employed. After the produced modeling system has been usedthe first hollow body is disposed of and the second hollow body isavailable for re-use. It is especially expedient here if both hollowbodies are basically transparent.

As per another preferred implementation form of the manufacturing methodin accordance with the invention a second hollow body is used whichconsists of at least two portions which can be interconnected with eachother and at least partially disconnected, the connection of which is atleast partially separated to allow the first hollow body to beaccommodated prior to the method being carried out and removed afterimplementation of the method has been completed. The second hollow bodymay thus consist of two portions that can be completely disconnectedfrom each other or, in accordance with a particularly preferredembodiment, may comprise two rotatably connected parts so that the bodycan be snapped open or close. For the accommodation of the first hollowbody the second hollow body is opened and then closed again beforeheating and generation of the deformations takes place.

For this purpose combinations of metal plates or plates of some othersuitable material as well as suitable foils, especially plastic foils,may expediently be used. Particularly expedient are molding die platesthat can be heated and are thus capable of heating up the foil material.The heated foil material can then be exposed to pressure and/or vacuumso that the first hollow body is produced.

Pressure and/or vacuum may in this case be employed to produce a firsthollow body tailored to satisfy individual requirements.

After the deformations have been created and, if thought necessary, thefirst hollow body has been closed off so as to be air-tight (especiallyby bonding or welding) the second hollow body can simply be snapped openenabling said first body to be easily removed. In this case, the secondhollow body functions in the same way as a molding die.

Such a design of the second hollow body offers the advantage in that itis also well suited for implementing the method in combination withfirst hollow bodies that do not have the form of tubes. It isparticularly expedient for the cut-outs to extend over both parts of thesecond hollow body so that the edges of the hollow body forming thecut-outs come apart when the second hollow body is opened resulting inthe cut-outs to widen upon opening the second hollow body. In thisembodiment the first hollow body can be taken out of the second hollowbody after the deformations have been created without running the riskof damaging the first hollow body and the deformations produced.

For the creation of artificial aneurysms it is beneficial if localheating is applied in the form of heat directed to spots of a predefinedsmall area. It is particularly appropriate in this context if the secondhollow body has at least one cut-out and the first hollow body havingbeen introduced into the second hollow body is heated in a spot-likemanner from the outside in at least one of the areas located under thecut-outs prior to being subjected to pressure.

An additional advantage of the method according to the invention is thataside from protuberances other deformation types and in this way othertypes of vascular malformations can be simulated. For example, modelsystems of stenotic vessels can thus be produced that comprisedeformations corresponding to vessel sections which are not constrictedwhereas sections of the first hollow body remain in their original stateand thus represent the stenotic segment. In this way not only can localconstrictions characteristic of stenotic areas be reproduced but alsothe elasticity and thickness of the vessel walls which show majordifferences in the stenotic and physiologically sound segments. For thispurpose a second hollow body is most expediently used. It isparticularly advantageous to employ a tubular second hollow body and afirst one comprising a hose segment whose shape fits in a form-closedmanner into the second hollow body of tubular design, with thelongitudinal dimension of said first body exceeding the length of thesecond hollow body so that after a partial area of the hose segment hasbeen placed inside the tube and such partial area or areas of the hosesegment not located inside the tube have been subsequently heated up andsubjected to pressure a dilatation of this or these areas will takeplace. However, the non-heated partial area which is embraced by theform-closed tube will maintain its original diameter as well as itsoriginal wall thickness.

Furthermore, the invention relates to a modeling system for vascularmalformations which is manufactured in accordance with the abovedescribed method. Preferred in this context are vascular models foraneurysms and/or stenoses. Especially expedient here is a modelingsystem according to the invention wherein the thickness of the wallsthat enclose the hollow space of the hollow body and/or the diameter ofthe first hollow body essentially correspond to the dimensioning ofblood vessels as they exist in humans or animals. The dimensioning withrespect to inside diameter, wall thickness or overall diameter in thiscase depends on the type of vessel or vessels to reproduced by themodel. Such a dimensioning may vary from modeling system to modelingsystem and in the case of complex modeling systems even dimensioning ofthe different artificial vessels may vary greatly. Surely, ananeurysm-carrying vessel located close to the aorta has other dimensionsthan a cerebral endartery. However, these dimensions are sufficientlyknown to the above mentioned average person skilled in the art. Testsperformed by the inventor showed that inside diameters ranging between0.5 and 30 mm and wall thicknesses between ≦0.3 and 4 mm areparticularly expedient. (These dimensions do not relate to thenon-deformed partial areas of the first hollow body. Same as the naturalvascular malformations the deformations may of course have significantlysmaller wall thicknesses and significantly greater inside diameters.)

Simple modeling systems which basically consist of a pathway or a hosewherein a deformation has been created are particularly inexpensive.More complex modeling systems serve to represent communicating vesselsystems which are very well suited to simulate and clarify, for example,the influence the main blood flow vectors have on constricted ordilatated vascular segments or protuberances.

Furthermore, the invention relates to an arrangement consisting of amodeling system according to the invention and a liquid pumping systemthat serves to supply a liquid to the modeling system. In an especiallypreferred embodiment an isotonic common salt solution, artificial bloodor fresh blood is used as liquid or any other liquid that is eitherespecially inexpensive or, to the extent possible, has characteristicscomparable to natural blood.

Which type of pumping system is to be used depends on the effects thatare intended to be achieved and can be easily selected by the abovementioned average person skilled in the art. Customary roller or pistondiaphragm pumps are cost-effective and permit hydrostatic pressures tobe generated that correspond to the natural blood pressure. In order tosimulate the cushioning properties of blood vessels peripheral resistorsthat can be regulated may expediently be arranged upstream and/ordownstream. The simulation of complex flow systems in the artificialvascular system (backflow, pulsatility, pressure and frequencyvariations, adapted to physiological and/or pathological conditionsexisting within the organism) may expediently be achieved with the aidof computer-controlled pumping systems (e.g. computer-controlledpiston-diaphragm pumps). In this case it is especially appropriate touse a pumping system that enables pressure of variable intensity to beapplied. It is also considered expedient if the pumping system permitsliquid to be applied in a manner that enables a hydrostatic pulse to begenerated the frequency and/or rhythm of which can be varied. To enablethe inventive arrangement to be used in conjunction with nuclearmagnetic resonance imaging (NMR) it is expedient for the pumping systemto be constructed of non-magnetic components and, for example, consistentirely of plastic material. The drive in this case may, for example,be located outside the tomograph or be of pneumatic type.

In accordance with another expedient embodiment the arrangementaccording to the invention is equipped with a visual recording system.For this purpose conventional video systems with enlarging lenses ordigital recording systems are suited. If thought appropriate imagingmethods may be employed in this context such as computed tomography,MLT, NMR or other methods known to the above referred to skilled person.

The invention furthermore relates to the use of a modeling systemaccording to the invention or an inventive arrangement in the medicalfield. They are in particular suited for the examination of the effectsof medicine influencing blood coagulation or thrombosis; thedevelopment, testing or improvement of medical appliances for thetherapy of vascular malformation preferably aneurysms; the development,testing or improvement of medical treatment methods for the therapy ofaneurysms in vitro; the basic and advanced training of physicians orother health personnel, or the analysis of the flow conditions existingin and around vascular malformations.

For example, a simulation and examination of the flow characteristics ofblood in aneurysms and stenotic vessels may be carried out preferably byintroducing a contrast medium and performing a simultaneous analysisusing one of the above described image-forming methods. In this way itis also possible to examine new contrast media and their spreadingbehavior within the vascular system in the event of vesselmalformations. For the purpose of visualizing hemodynamic spreadingcharacteristics it is therefore expedient if the contrast medium usedand the carrier liquid representing the blood are of different color.

The invention shall now be described in more detail by way of preferredembodiment examples as shown in the following figures.

FIG. 1 is an enlarged side view of a simple aneurysm hose model 1;

FIG. 2 illustrates the steps involved in the production of a two-shellmodeling system 1′ for aneurysms in enlarged and schematicrepresentation;

FIG. 3 is the enlarged schematic representation of how an artificialaneurysm 3 is generated with the help of a molding die 11;

FIG. 4 shows schematically and as an enlarged representation the stepsinvolved in the production of a modeling system 1 for vessel stenoses.

FIG. 1 represents a modeling system 1 for an aciniform aneurysm of anintracranial artery which is made of a PVC hose 2. The elastic PVC hose2 has an inside diameter of 1.5 mm and a wall thickness of 0.65 mm. Forthe purpose of reproducing the artificial aneurysm 3 the hose 2 waslocally (spot-wise) heated by means of a gas flame to a temperature inthe softening range of the PVC material. At the same time using aconventional pressure pump the hose was filled with compressed air at apressure of 0.5 bar resulting in the artificial aneurysm 3 to form atthe locally heated spot. Subsequently, the artificial aneurysm 3together with the gas present within the aneurysm was cooled down.Cooling was carried out with slight pressure being appliedsimultaneously to prevent the aneurysm from collapsing prematurely.Finally, both ends 4/4′ of hose 2 were sealed off so as to be air-tightby welding under slight pressure so that the artificial aneurysm 3remained stable for a longer period of time.

As far as elasticity and structure are concerned the artificial aneurysm3 resembles natural aneurysms, especially because it consists offlexible material and its wall 5 reduces significantly from the base ofthe aneurysm 6 towards the dome 7. Similar to the natural situationfound in the human blood system the rather thin-walled dome 7 of theartificial aneurysm 3 is particularly fragile, said fragility evenincreasing when pressure is applied through the introduction of liquid.

The modeling system 1 shown is particularly suited for testing noveltherapy forms and diagnostic methods as well as for training purposes.Both ends 4/4′ of hose 2 are cut open and connected, so as to beconductive, with a liquid pumping system, for example a diaphragm pistonpump. The connection is made by joining hose 2 to the pump using aY-type coaxial sealing system hooked up to the ends of hose 2. Byapplying pressure in a pulsating manner with artificial blood heated to38° C. the human pulse is simulated. For this purpose hydrostaticpressures ranging from 50 to 250 mm Hg are generated. To enablepressure, frequency and rhythm of the liquid applied in a pulsatilemanner to be varied a computer is provided and used in conjunction withthe pump so that various physiological and pathological conditions ofthe circulation system can be simulated.

In this case the modeling system 1 with the exception of its two hoseends 4/4′ is placed in a basin filled with a liquid heated to 38° C.Since the artificial blood and the liquid into which the modeling system1 has been immersed have been heated up endovascular instruments andmechanical occlusion devices behave very much like being located in thebody as far as their bending characteristics and torsional stability areconcerned. The same applies to the elasticity of the hose 2 representingthe vessel on which the aneurysm is located. Embedding the modelingsystem 1 in surrounding liquid will, for example, result in an externalresistance affecting the “surge tank” properties of hose 2 and thepulsatile behavior of the aneurysm 3.

For the purpose of implementing the endovascular method which is to bedeveloped, tested or learned the user introduces, for example, amicro-catheter via a hemostatic valve with Y-type branch into the openhose 2 and guides it towards the base 6 of the artificial aneurysm 3. Atthis point, placement of a polymerizing material or an occlusion spiralis effected, for example. Since both the hose 2 representing the vesseland the artificial aneurysm 3 are designed so as to be elastic and havesurface characteristics similar to that of natural blood vessels oraneurysms mistakes in guiding and/or introducing the occlusion materialinto the artificial aneurysm 3 can be better detected than withcustomary glass modeling systems. In this way, the surgeon will feel ifthe moved object abuts or gets caught within the hose 2 and, moreover,there may also be the risk that a severely traumatizing action willcause a rupturing of the artificial aneurysm 3. Due to the fact that themodeling system 1—same as conventional glass systems—is transparent itfurthermore offers the advantage that endovascular maneuvering may beeasily viewed from the outside and, if thought necessary, recorded.

FIG. 2 is a schematic representation of the steps involved in themanufacture of a two-shell modeling system 1′ for aneurysm. To createthe two-shell modeling system 1′ in accordance with the invention anelastic polyethylene hose 2 of an inside diameter and wall thicknesstypical of the vessel to be reproduced is placed into a copper tube 9having ellipsoidal and annular cut-outs 8 of various dimensions, theinner lumen of said tube being sized such that it is suited toaccommodate the polyethylene hose 2 in a form-closed manner. After thepolyethylene hose 2 has been pushed into the copper tube 9 (see FIG. 2b) it is locally heated spot-wise from the outside by a precisely dosedexposure to microwaves until the softening point of polyethylene hasbeen reached. The spotwise heating from the outside is applied to apartial area of the polyethylene hose 2 which is accessible from theoutside through one of the cut-outs 8 provided in the copper tube 9.Prior to heating, one end 4′ of the polyethylene hose 2 is closed off byfusing so as to be tight to air. Following this the other end 4 isconnected with a conventional diaphragm piston pump via a coaxialsealing system in a manner so as to be conductive.

After heating has taken place and the softening point of the materialreached pressure is applied by means of the diaphragm piston pump whichhas been set to inject a defined amount of air into hose 2 for apredetermined period of time. This not only determines the size of thedeformation to be created but also makes sure that the soft spot willremain intact and will not break as a result of too high a pressurebeing applied or dilatation taking place too quickly. Due to pressurebeing applied to the hot spot a deformation will form as illustrated inFIG. 2 c, said deformation constituting the artificial aneurysm 3.Similarly, the creation and modulation of the deformation may be broughtabout by applying vacuum externally to the hose (or making use of acombination of applying pressure internally and creating a vacuumexternal to the hose). Subsequently, the two-shell model 1′ generated inthis way may be employed directly for the teaching or development ofmedical techniques or prepared for later use by welding and thus sealingoff the still open end 4 in a manner to be air-tight.

The two-shell model 1′ shown in FIG. 2 c is particularly suited for theexact replication of vessel segments located before and after theaneurysm (e.g. in the form of defined convolutions or, as illustrated inthe figure, as a precisely straight vascular run). Moreover, thistwo-shell model 1′ enables the size of the neck of the aneurysm 6 and ofthe aneurysm 3 to be exactly determined. When the two-shell model 1′shall be used the two closed off ends 4/4′ are opened up and liquid isinjected into the model 1′. Afterwards, the flexible hose 2 carrying theaneurysm 3 can simply be removed from the copper tube 9 and disposed of.The copper tube 9 on the other hand can be reused many times. It is alsoexpedient if the copper tube 9 is provided with a longitudinallyarranged seam along which it can be folded open (refer to the exampleshown in FIG. 3).

FIG. 3 illustrates the steps involved in the manufacture of artificialaneurysms based on a three-dimensional system of communicating hoses, ofwhich only portion 10 has been shown here. In the same way an aneurysmmodel system may of course be produced using a single hose (analogouslyto what has been shown in FIG. 2 as an example). In this example thedesired artificial aneurysms 3 are produced with the help of a tubularmolding die 11. This die consists of two parts 12/12′ which areconnected at one edge by means of a hinge joint 12 allowing a foldingmovement of both portions so that the molding die 11 can be opened orclosed by appropriately slewing the two parts 12/12′ either against oraway from each other. To place the tubular partial area 10 of thethree-dimensional system of communicating hoses into the molding die 11the molding die 11 is opened. It is closed again after the partial area10 has been placed in position. For the purpose of closing the two parts12/12′ of the molding die 11 firmly at the edges not connected by thehinge joint 13 they are provided with latch-type connections which canonly be disengaged by applying a slight mechanical pressure. In this waythe molding die 11 is prevented from being opened through thepressurizing action occurring while the artificial aneurysm 3 isproduced. On the other hand, this connection allows the two parts 12/12′to be easily separated.

Cut-out 8 which is used to predetermine the form of the artificialaneurysm 3 to be produced is located on both parts 12/12′ of the moldingdie 11 such that it spans over the free edges of the two parts 12/12′.After the artificial aneurysm 3 has been formed the partial area 10together with the artificial aneurysm 3 produced may easily be removedfrom the opened molding die 11. Molding dies 11 in which several,possibly differently sized cut-outs 8 are located along the free edgesof the die portions are also considered expedient because this wouldpermit one or several and/or, if necessary, differently dimensioned orpositioned aneurysms 3 to be produced as desired with a single moldingdie 11.

After closing the molding die 11 and heating up the partial area 10 at adefined spot located under the cut-out 8 an aneurysm of predeterminedsize is produced by applying pressure (see arrow, FIG. 3 b).Subsequently, the partial area 10 is removed from the molding die 11which for this purpose is first opened, as illustrated in FIGS. 3 c and3 d. The three-dimensional system of communicating hoses may then be putto use without the molding die 11. By way of the method shownschematically artificial aneurysms of a predetermined sizing of the neck6 can be produced (refer to FIGS. 3 d and 3 e). When the aneurysm 3 hasbeen produced further vascular malformations or aneurysms may becreated, if necessary, on the same or other partial areas of thethree-dimensional system of communicating hoses until the desiredmodeling system is complete.

The modeling system so generated is then placed in a basin filled withhardening gel so that after the gel has cured or set thethree-dimensional form of the system is stabilized without the modelsystem's elasticity being completely impaired. The gel also serves as akind of peripheral resistance and cushioning of the “surge tank”characteristics comparable to tissue or cerebrospinal fluid surroundingthe cerebral vessels so that such an arrangement is particularly suitedwhen cerebral vascular networks are to be reproduced.

FIG. 4 shows an example of how a modeling system 14 for stenotic vesselsis produced. For this purpose a flexible polyethylene hose 2 having aninside diameter of 6.0 mm and a wall thickness of 1.5 mm is placed in aform-closed molding die 11 that can be folded open. Following this,segments 17 of hose 2 which are not surrounded by the molding die 11 areheated locally from the outside by means of hot paraffin oil until thesoftening point has been reached and are then dilatated by applyingpressure. As shown in FIG. 4 the molding die is then opened and themodeling system 14 so generated is removed after the molding die 11 hascooled down. Furthermore, as can be seen from FIG. 4 d the modelingsystem 14 does not only simulate the differing sizing of the inner lumenof stenotic vessels but also the different thickness of the vessel wall15 and 15′ of the stenotic 16 and physiological segments 17. As a resultof the different wall thicknesses the elasticity characteristics of thevarious vessel segments 16/17 differ as well in the modeling system ofstenotic vessels 14 to reflect conditions as actually existing in thebody.

1. Method for the generation of a modeling system for vascularmalformations (1), characterized by the following steps: a) localheating of first hollow body which is suited for conducting liquid andconsists, at least in one or more partial areas, of a flexible,thermoplastically deformable material, such local heating being effectedon at least one of the partial areas until the thermoplasticallydeformable material softens, and b) subjecting the first hollow body toa pressure that is high enough to cause a deformation at the heatedlocation, with the size of the deformation being governed by theduration of the pressure applied and/or by the intensity of the pressureapplied.
 2. The method according to claim 1, characterized by a hermeticclosure of the first hollow body subjected to gas pressure after thedeformation has been produced.
 3. The method according to claim 2,characterized in that the closure is effected by fusing or bondingtogether the openings of the first hollow body.
 4. Method according toclaim 1, characterized in that at least the deformation produced andpreferably the entire first hollow body is designed so as to betranslucent or basically transparent.
 5. The method according to claim1, characterized in that the entire hollow body consists of flexiblematerial.
 6. The method according to claim 1, characterized in that theentire hollow body consists of thermoplastically deformable material. 7.Method according to claim 6, characterized in that the thermoplasticallydeformable material is PVC, PUR, PP or PE.
 8. The method according toclaim 1, characterized in that the local heating is brought about by thelocal effect caused by a hot liquid, preferably a lipophilic liquidhaving a high boiling point, through the local effect caused by a flame,preferably a flame generated by a gas torch, through the localapplication of a hot wire, preferably a wire spiral or coil, or throughthe locally confined exposure to microwaves.
 9. The method according toclaim 8, characterized in that the local heating is achieved through theapplication of a heat source external to the hollow body.
 10. The methodaccording to claim 15, characterized in that the second hollow body isof heatable construction and also effects heating of the first hollowbody.
 11. The method according to claim 1, characterized in that thefirst hollow body is a system of two-dimensionally arranged pathwayscommunicating with each other, or part of such a system.
 12. The methodaccording to claim 11, characterized in that the system is produced bysticking together sectionally two plastic foils arranged one on top ofthe other by welding or bonding methods.
 13. The method according toclaim 12, characterized in that the plastic foils are made of tearproofmaterial.
 14. The method according to claim 1, characterized in that thefirst hollow body is designed as a hose (2), system of communicatinghoses or part (10) of such a system.
 15. A method according to claim 1,characterized in that the first hollow body, prior to heating, is placedat least partially into a second hollow body consisting of a materialthat cannot be thermoplastically deformed with at least a partial areaof the second hollow body accommodating at least a partial area of thefirst hollow body in a form-closed manner.
 16. The method according toclaim 15, characterized in that the second hollow body is provided withat least one cut-out (8).
 17. The method according to claim 16,characterized in that the cut-out has an ellipsoidal or annular shape.18. Method according to claim 15, characterized in that the secondhollow body is of one-piece construction and the first hollow bodyremains in it after the deformations have been produced.
 19. Methodaccording to claim 15, characterized in that the second hollow bodyconsists of at least two portions (12) which can be interconnected witheach other and at least partially disconnected, the connection of whichis at least partially separated to allow the first hollow body to beaccommodated prior to the method being carried out and removed afterimplementation of the method has been completed.
 20. The methodaccording to claim 19, characterized in that the second hollow bodyconsists of two parts (12) that are slewably connected and can besnapped open or close.
 21. Method according to claim 15, characterizedin that the second hollow body has a primarily tubular form.
 22. Methodaccording to claim 15, characterized in that the local heating isapplied in a spotwise manner.
 23. The method according to claim 22,characterized in that the second hollow body has at least one cut-outand the first hollow body having been introduced into the second hollowbody is heated in a spot-like manner from the outside in at least one ofthe areas located under the cut-outs.
 24. The method according to claim21, characterized in that the first hollow body comprises a hose segmentthat fits in a form-closed manner into the second hollow body of tubulardesign, with the longitudinal dimension of said first body exceeding thelength of the second hollow body so that after a partial area of thehose segment has been placed inside the tube and such partial area orareas of the hose segment not inside the tube have subsequently beenheated up and subjected to pressure a dilatation of this or these areaswill take place, with the non-heated partial area which is embraced bythe form-closed tube will maintain its original diameter as well as itsoriginal wall thickness.
 25. A modeling system for vascularmalformations formed by the method comprising the steps of: a) localheating of first hollow body which is suited for conducting liquid andconsists, at least in one or more partial areas, of a flexible,thermoplastically deformable material, such local heating being effectedon at least one of the partial areas until the thermoplasticallydeformable material softens, and b) subjecting the first hollow body toa pressure that is high enough to cause a deformation at the heatedlocation, with the size of the deformation being governed by theduration of the pressure applied and/or by the intensity of the pressureapplied.
 26. The modeling system according to claim 25, characterized inthat the thickness of the walls (15) that enclose the hollow space ofthe first hollow body and/or the diameter of the first hollow bodycorrespond to the dimensioning of blood vessels as they exist in humansor animals.
 27. Arrangement comprising a modeling system according toclaim 25 as well as a pumping system for filling the modeling systemwith liquid.
 28. The arrangement according to claim 27, characterized bya visual recording system.
 29. Arrangement according to claim 27,characterized in that at least part of the modeling system is embeddedin a liquid or gel.
 30. Arrangement according to claim 27, characterizedin that the liquid filled in is an isotonic common salt solution,artificial blood or fresh blood.
 31. Cancelled.
 32. The modeling systemaccording to claim 25, characterized by a hermetic closure of the firsthollow body subjected to gas pressure after the deformation has beenproduced.
 33. The modeling system according to claim 32, characterizedin that the closure is effected by fusing or bonding together theopenings of the first hollow body.
 34. The modeling system according toclaim 25, characterized in that at least the deformation produced andpreferably the entire first hollow body is designed so as to betranslucent or basically transparent.
 35. The modeling system accordingto claim 25, characterized in that the entire hollow body consists offlexible material.
 36. The modeling system according to claim 25,characterized in that the entire hollow body consists ofthermoplastically deformable material.
 37. The modeling system accordingto claim 36, characterized in that the thermoplastically deformablematerial is PVC, PUR, PP or PE.
 38. The modeling system according toclaim 25, characterized in that the local heating is brought about bythe local effect caused by a hot liquid, preferably a lipophilic liquidhaving a high boiling point, through the local effect caused by a flame,preferably a flame generated by a gas torch, through the localapplication of a hot wire, preferably a wire spiral or coil, or throughthe locally confined exposure to microwaves.
 39. The modeling systemaccording to claim 38, characterized in that the local heating isachieved through the application of a heat source external to the hollowbody.
 40. The modeling system according to claim 45, characterized inthat the second hollow body is of heatable construction and also effectsheating of the first hollow body.
 41. The modeling system according toclaim 25, characterized in that the first hollow body is a system oftwo-dimensionally arranged pathways communicating with each other, orpart of such a system.
 42. The modeling system according to claim 41,characterized in that the system is produced by sticking togethersectionally two plastic foils arranged one on top of the other bywelding or bonding methods.
 43. The modeling system according to claim42, characterized in that the plastic foils are made of tearproofmaterial.
 44. The modeling system according to claim 25, characterizedin that the first hollow body is designed as a hose (2), system ofcommunicating hoses or part (10) of such a system.
 45. The modelingsystem according to claim 25, characterized in that the first hollowbody, prior to heating, is placed at least partially into a secondhollow body consisting of a material that cannot be thermoplasticallydeformed with at least a partial area of the second hollow bodyaccommodating at least a partial area of the first hollow body in aform-closed manner.
 46. The modeling system according to claim 45,characterized in that the second hollow body is provided with at leastone cut-out (8).
 47. The modeling system according to claim 46,characterized in that the cut-out has an ellipsoidal or annular shape.48. The modeling system according to claim 45, characterized in that thesecond hollow body is of one-piece construction and the first hollowbody remains in it after the deformations have been produced.
 49. Themodeling system according to claim 45, characterized in that the secondhollow body consists of at least two portions (12) which can beinterconnected with each other and at least partially disconnected, theconnection of which is at least partially separated to allow the firsthollow body to be accommodated prior to the method being carried out andremoved after implementation of the method has been completed.
 50. Themodeling system according to claim 49, characterized in that the secondhollow body consists of two parts (12) that are slewably connected andcan be snapped open or close.
 51. The modeling system according to claim45, characterized in that the second hollow body has a primarily tubularform.
 52. The modeling system according to claim 45, characterized inthat the local heating is applied in a spotwise manner.
 53. The modelingsystem according to claim 52, characterized in that the second hollowbody has at least one cut-out and the first hollow body having beenintroduced into the second hollow body is heated in a spot-like mannerfrom the outside in at least one of the areas located under thecut-outs.
 54. The modeling system according to claim 51, characterizedin that the first hollow body comprises a hose segment that fits in aform-closed manner into the second hollow body of tubular design, withthe longitudinal dimension of said first body exceeding the length ofthe second hollow body so that after a partial area of the hose segmenthas been placed inside the tube and such partial area or areas of thehose segment not inside the tube have subsequently been heated up andsubjected to pressure a dilatation of this or these areas will takeplace, with the non-heated partial area which is embraced by theform-closed tube will maintain its original diameter as well as itsoriginal wall thickness.